Commonly prevailing as a digital duplicator high in printing speed and low in running cost is a printing machine in which a master is produced by melt-perforating a thermoplastic resin film layer of a heat sensitive stencil sheet by use of a heating means such as a thermal printing head which generates heat in a dot-like pattern in accordance with character or image information converted into electric signals, and in which the stencil sheet is wound around a circumferential surface of a printing drum so that an ink is transferred from the printing drum to a printing sheet through the perforated stencil sheet.
The digital duplicator known in the art requires a device for storing and conveying the heat-sensitive stencil sheet as well as a used-stencil discharging device. When printing is performed based on a new original, a used-sheet must be discarded. Usually, the used-stencil is temporarily stored in a used-stencil discharge box, and then is disposed when the box is full of used-stencils. This is because, in the conventional stencil printing, stencil sheets used as printing plates cannot be regenerated or reused.